Cable sealing

ABSTRACT

A joint between a mass-impregnated paper insulated cable and a plastic insulated cable is sealed to contain the mass impregnating, oil material by applying a heat-recoverable oil resistant tubing over the exposed paper insulation so as to leave a portion thereof uncovered adjacent the exposed conductor of the cable, applying an oil resistant mastic to said uncovered portion of the insulation and over an adjacent end of said tubing, and applying a further heat-recoverable tubing over the mastic and an adjacent portion of the oil resistant tubing.

This application is a continuation of application Ser. No. 902,115,filed Aug. 29, 1986, now abnadoned, which in turn is a continuation ofapplicaiton Ser. No. 644,821, filed Oct. 29, 1984, now abandoned, whichin turn is a continuation of application Ser. No. 365,086, filed Apr. 2,1982 which is now U.S. Pat. No. 4,485,269.

DESCRIPTION

This invention relates to cable sealing, and is particulary concernedwith sealing the end of a mass-impregnated paper insulated cable, at ajoint or termination. The invention finds particular, though notexclusive, application in a transition joint between a mass-impregnated(MI) paper insulated cable and a plastic insulated cable, for example,in the medium voltage range of 12 to 17.5 KV.

Plastic, usually cross-linked polyolefin, for example polyethylene,cable is being used more and more throughout the world, and problemshave arisen in jointing this to existing mass-impregnated paper cablebecause of the difficulty in satisfactorily sealing themass-impregnating material. Such material comprises blends of synthetichydrocarbon resins and mineral oils, usually incorporating naturalresin. For convenience elsewhere herein, such material will be referredto as "oil". The viscosity of this material typically is around 10,000mm² /sec (kinematic viscosity) at room temperature and decreases toaround 200 mm² /sec at the maximum operating temperature of the cable,polyethylene to deterioriate, causing it to soften and swell, and thatan oil-resistant barrier must be provided to protect such material.

Some cross-linked polyolefin electrically insulating materials, however,have good oil resistance, and have been used very successfully for someyears in the form of recoverable, for example heat-recoverable, tubingand breakouts in low-voltage (i.e. around 1 kV) MI/plastic cabletransition joints and low voltage MI cable terminations. Such componentsare commercially available from Raychem. At higher voltages suchmaterials are still applicable, but higher voltage joints orterminations may require conductive and semi-conductive materials toensure proper electrical integrity, for example to providestress-control. Conductive polymers are widely used in many types ofplastic cable and accessories for electrical field control and screeningpurposes. However, conductive polymers are heavily loaded with carbonand are very susceptible to oil uptake, drastically increasing theirresistance. The resultant loss of electric field control can lead tosurface discharge and, ultimately, complete electrical breakdown of thecable accessory or of the cable itself. Thus, where conductive polymersare used in connection with MI cable, it is even more important toprovide an oil barrier.

It is an object of the present invention to provide an improved methodof sealing the mass-impregnating material of an MI cable at an endthereof, to facilitate its jointing to a plastic cable or itstermination, for example.

In accordance with one aspect of the present invention, there isprovided a method of sealing an end of a mass-impregnated paperinsulated cable, the cable end being stripped to expose a conductorthereof and to expose a length of the overlying mass-impregnated paperinsulation, the method comprising enclosing said exposed insulationwithin a recovered first polymeric member that is substantiallyunaffected (as herein defined) by the mass-impregnating material of thecable so as to leave exposed a portion of said length of insulationadjacent said exposed conductor, applying a sealant material, which issubstantially unaffected by the mass-impregnating material of the cable,over said exposed portion of the cable insulation, and over an adjacentend region of said first polymeric member, and recovering a secondpolymeric member over said sealant material and an adjacent portion ofsaid first polymeric member.

As herein used, "recoverable" refers to a property of an article wherebyits configuration, for example its dimensions, may be made to changesubstantially when subjected to an appropriate treatment. The articlemay be, for example, heat recoverable such that its configurationchanges when it is subjected to a heat treatment. Heat-recoverablearticles may be produced by deforming an article from a dimensionallyheat stable configuration to a dimensionally heat unstableconfiguration, in which case the article will assume, or tend to assume,the original heat stable configuration on the application of heat alone.According to one method of producing a heat recoverable article, apolymeric material is first extruded or moulded into a desired shape.The polymeric material is then cross-linked or given the properties of across-linked material by exposure to high energy radiation for example ahigh energy electron beam or gamma radiation. The crosslinked polymericmaterial is heated and deformed, and then locked in the deformedcondition by quenching or other suitable cooling means. The deformedmaterial will retain its shape almost indefinitely until exposed to atemperature above its crystalline melting temperature, for example about120° C. in the case of polyethylene. Examples of heat-recoverablearticles may be found in U.S. Pat. No. 2,027,962 and in U.K. Patentspecification No. 990,235, the disclosures of which are incorporatedherein by reference. As is made clear in U.S. Pat. No. 2,027,962,however, the original dimensionally stable heat-stable configuration maybe a transient form in a continuous process in which, for example anextruded tube is expanded, whilst hot, to a dimensionally heat unstableform.

The term "substantially unaffected" as used herein with reference topolymeric members or sealant material is to be understood to mean thatthe mass-impregnating material of the cable has no effect thereon thatappreciably changes the electrical or mechanical properties thereof. Amember or material that is so substantially unaffected is also hereinreferred to as "oil resistant".

It has been found, very surprisingly, that the most efficient sealing ofsuch a cable end is achieved by recovering the second polymeric membernot only over the overlap between the sealant material and the firstpolymeric member but also directly on to an adjacent portion of thefirst polymeric member, thereby to provide a direct seal between the twopolymers, preferably of between about 19 mm and about 40 mm. On theother hand, and contrary to expectation, the sealing of the massimpregnating material has been found to be quite unsatisfactory (a) whenno sealant material is used at the edge of the first polymeric member,since surface imperfections in the overlying polymer surfaces could giverise to leakage paths, and (b) when sealant material is provided overthe whole of the overlap between the two polymeric members, cohesivefailure then being experienced.

The sealing thus provided retains the impregnating material of the paperinsulated cable so that other components, that are adversely affected bythe impregnating material, and in particular components made ofconducting or semiconducting polymeric materials, may subsequently besafely applied to the cable.

It will be appreciated that since the second polymeric member isseparated from the mass-impregnated paper insulation by the firstpolymeric member and/or the sealant material, it may be made from anymaterial chosen for its electrical or other properties without having toensure that it is unaffected by the mass-impregnating material. Inparticular, it may be made from a material that is electricallyconductive or semi-conductive, if the voltage rating of the cable sorequires, for example.

In a cable joint or termination that requires an electrically conductiveor semi-conductive layer to extend around the cable insulation away fromthe exposed conductor, this may be provided to overlap the said firstpolymeric member, to be sealed thereto at its free edge by oil-resistantsealant material, for example the said sealant material, and said secondpolymeric member may be arranged to overlap the said edge. Conveniently,this layer may be provided by a third recoverable member. In sucharrangements, it has been found advantageous to have asurface-to-surface overlap between said first and second members of atleast about 19 mm, preferably 20 mm, and up to about 40 mm. Overlapstowards the larger end of this range are particularly applicable wherethe first member extends substantially to the end of the paperinsulation of the cable, or substantially to the beginning of itstapering down towards the conductor, when such profiling is present;this being the case when electrical connection is made to the connectorby means, for example crimping that is not harmful to a nearby polymericmember. When electrical connection is made by soldering, for example, inorder to avoid heat damage it is desirable to space the first polymericmember relatively further axially away from the conductor, therebyleading to an overlap of a size towards the smaller end of theabovementioned range.

Preferably, the sealant material is arranged to overlap the firstpolymeric member at said edge adjacent the cable conductor by betweenabout 15 mm and 25 mm after the second polymeric member has beenrecovered thereover. In a method in which the second polymeric member isrecovered over the said third polymeric member and further sealantmaterial is provided at the edge between the first and third members,the said further sealant material preferably extends for between about10 mm and 20 mm along the first member from said edge, thereby toenhance the containment of the impregnating material of the paperinsulated cable.

The second polymeric member may comprise semi-conductive or conductivematerial by consisting of a homogeneous member or by being the innermember of a two-part member. In particular, the second member maycomprise a two-part member whose inner part comprises semi-conductivematerial and whose outer part comprises insulating material.

The sealant material may be applied integrally with one of said firstand second polymeric members.

A further one or more recoverable polymeric members may be recoveredover said second member.

One or more, and preferably all, of the polymeric members may be ofgenerally tubular configuration, and where the second member is atwo-part member this may be formed as a co-extrusion, or by moulding.Furthermore, one or more, and preferably all, of the polymeric membersmay be cross-linked, and preferably heat-recoverable, members, made, forexample, from polyolefin material.

The sealant material may be an adhesive or a mastic, but advantageouslyit comprises an oil-resistant mastic, and preferably has a viscosity at25° C. (room temperature) of between 2×10⁵ and 1×10⁶ Pa-sec.(dynamicviscosity) and at 70° C. (typical maximum operating temperature of thecable) of between 1×10⁴ and 2×10⁵ Pa-sec.

In accordance with another aspect of the present invention, there isprovided a method of sealing a joint between a first cable comprising amass-impregnated paper insulated cable and a second cable comprising aplastic insulated cable, wherein an end of said first cable is strippedto expose a conductor thereof and to expose a length of the overlyingmass impregnated paper insulation, and wherein a first recoverablepolymeric member that is substantially unaffected by themass-impregnating material is recovered on to the impregnated paperinsulation to leave exposed a portion thereof adjacent the baredconductor of the first cable, oil-resistant sealant material is appliedto enclose completely said exposed insulation and to overlap theadjacent first polymeric member and bared conductor, and a secondrecoverable polymeric member is recovered so as to extend over saidsealant material and to be in direct contact with said first polymericmember.

Preferably, the direct contact between said first and second polymericmembers extends axially of the first cable for a length of between about20 and 40 mm.

Preferably the first polymeric member is overlapped by the sealantmaterial for between about 15 mm and 25 mm.

The second polymeric member may be electrically semiconducting orconducting, this being particularly advantageous at voltages above about1 kV, say between 12 and 17.5 kV, to effect stress-control.

Preferably, the second polymeric member extends from the first cableacross the joint between the conductors of the first and second cables,and on to the insulation of the second cable.

The sealant material may advantageously extend from the first cableacross the joint between the conductors of the first and second cables,and over any exposed portion of the conductor of the second cable.

The sealant material and polymeric members are preferably as describedabove with reference to said one aspect of the invention.

Advantageously, the oil-resistant first polymeric member is of amaterial sold under the trade name KYNAR, but Viton fluorocarbon rubber,silicone rubber, and nylon compositions, amongst others, are possiblesuitable alterations. During operation of the cable, the oil becomesheated thus generating a pressure within the cable. In general, theabove-mentioned alterations have poorer pressure retention qualitiesthan KYNAR, the important characteristic in this context is thestiffness of the polymeric member, and this can be achieved, forexample, by selecting a tubing with wall thickness of about 0.5 mm and aSecant Modulus of about 600 Mega Pascals, or a wall thickness of about 2mm having a Secant Modulus of about 150 Mega Pascals. Such tubing has astiffness such that it does not flex under oil pressure normallygenerated in operation.

In accordance with a further aspect of the invention, there is provideda method of breaking out the cores of a multi-core, for example threecore, cable used for connecting said cores to respective ones of aplurality of single core cables, in which a breakout is applied over theend of the multi-core cable, the cores are jointed together, a pluralityof recoverable protective components are recovered around respectiveones of the jointed cores and to overlap with respective end portions ofthe breakout, and a further recoverable protective component isrecovered so as sealingly to encompass said overlaps between thebreakout and said plurality of components, the entire breakout, and anadjacent portion of said single core cables.

It will be appreciated that sealed cables, transition joints, andbreak-out arrangements produced by the methods set out above are withinthe scope of the present invention.

A transition joint between a three-core mass-impregnated paper insulatedcable and a plastic insulated cable, suitable for use in the voltagerange 12 to 17.5 kV, will now be described, by way of example toillustrate the present invention, with reference to the accompanyingdrawings, in which:

FIG. 1 is a side elevation, partly in section, of one of the cores ofthe joint;

FIG. 1A is a partial section through part of a modified joint; and

FIG. 2 is a side elevation, partly in section, of a break-outarrangement for the cores of the three-core paper cable.

FIG. 1 shows a joint between one core, generally shown at 2, of athree-core mass-impregnated paper insulated cable and one core, showngenerally at 4, of a plastic insulated cable having three substantiallyidentical single cores.

The paper cable core 2 is stripped back to expose the impregnatedinsulating paper 6 that is chamfered at 8 down to an exposed conductor10 at one end thereof. In a corresponding manner, the plastic cable core4 is successively stripped back from its oversheath 12 to expose alength of its metal tape shield 14, semi-conductive tape screen 16,plastic insulation 18, which has conducting paint 20 applied theretoadjacent the semi-conductive screen 16, and conductor 22.

Since the mass-impregnating compound of the paper cable has a typicalviscosity value at room temperature of about 10,000 mm² /sec, this wouldtend to flow out of the cable after it has been stripped back so as toexpose the paper 6 and before completion of the joint. In this case, itmay be advantageous to apply an oil-resistant tape to extend between theexposed conductor 10 over the chamfer 8 and along the exposed length ofthe paper 6, thereby to provide a barrier that is temporarily-effectiveagainst oil drainage from the cable. Such taping may be avoided,however, if the following step in the process of jointing the cables iscarried out sufficiently soon after stripping of the paper cable. Aheat-recoverable polymeric tube 23 of electrically insulating materialthat is resistant to the mass-impregnating material of the core 2 isrecovered over the papers 6 from the position along the cable where theyare first cut back to an axial position slightly displaced from thelarger diameter of the chamfered portion 8 on the opposite side theretoof the conductor 10 to act as a barrier tube. Tubing sold under theTrade Name KYNAR has been found particularly suitable for this purpose.Where the above-mentioned oil-resistant tape has not been applied overthe whole length of the exposed paper 6, it may still be foundadvantageous to enclose that portion of the papers that would be leftexposed after recovery of the barrier tube 23.

Heat recoverable polyolefin tubings 24, 26, 28 and 30, for purposeshereinafter defined, are now slid in their unrecovered cylindricalstates over the plastic cable core 4 away from the joint area. The cableconductors 10 and 22 are introduced into respective ends of a metalferrule 32, and this is crimped so as to effect electrical connectionbetween the cable conductors.

Oil-resistant mastic 34 is then applied around the ferrule 32, over anyremaining exposed portions of the conductors 10 and 22, over the paper 6of the paper core 2 and so as to provide an overlap on to the oilbarrier tube 23 and on to the plastic insulation 18 of the respectivecables. The mastic 34 is applied over the above-mentioned areas to sealin the mass-impregnating material of the cable core 2, and to give asmooth exterior surface.

The recoverable tube 24, made of a conductive polymeric material soldunder the Raychem Trade Name CNTM, is then slid across the joint, overthe oil barrier tube 23, and is recovered thereonto at an axial positionspaced from the mastic 34. A further portion 36 of oil-resistant masticis applied around the end of the tube 24 at its overlap with tube 23.

The recoverable tube 26, which is stress-controlling and sold under theRaychem Trade Name SCTM, is then positioned across the cable joint suchthat it extends over the conductive tubing 24 on the core 2 and over themetal shield 14 on the core 4. The tube 26 is then heated to effect itsrecovery. Upon recovery of the tubing 26 over the oil-resistant mastic34 and 36, the mastic, having a viscosity at 25° C. of between 2×10⁵ and1×10⁶ Pa-sec, will become radially compressed and flow axially to acertain extent. The amount of mastic 34 and 36 applied is arranged to besuch that on recovery of the tubing 26, there are overlaps of about 15mm and 10 mm, respectively on the oil barrier tube 23. Furthermore, theoil barrier tube 23, conductive tube 24, and stress control tube 26 arearranged such that the direct polymer-to-polymer overlap between thetubes 23 and 26 is at least about 20+/-5 mm and at most about 40 mm. Asshown in the figure, this latter overlap is towards its maximum range,thus disposing the free end of the barrier tube 23 closely adjacent thechamfered paper pcrtion 8. However, where the electrical interconnectionof the conductors 10 and 22 is made by means such as soldering, wherebythe heat applied could adversely affect the closely adjacent oil barriertube 23, it is desirable that the oil barrier tube be terminated furtheraway from the chamfer 8, thus reducing the amount of overlap to a valuetowards the lower end of the range given above.

The overlaps referred to above have been found to provide very goodretention of the oil of the cable 2. This is so because flowable sealingis obtained where the tube 24 overlaps the tube 23 and where the tube 23overlaps the paper 6, so that any surface imperfections or otherdiscontinuities in the overlapping surfaces are filled in, and alsobecause the intermediate portion of direct polymer-to-polymer contactavoids the possibility of cohesive failure that would exist if themastic were to extend completely along the overlap between the tubes 23and 26.

It will thus be appreciated that the enclosing of the mass-impregnatedinsulating papers 6 by the oil barrier tube 23 and oil-resistant mastic34 seals in the mass-impregnating compound such that other components,in this case the conductive tube 24 and the stress control tube 26,which are adversely affected by the compound, may be safely applied tothe joint.

Finally, the tubing 28, made of insulating polymeric material is broughtover the joint and recovered and similarly the tubing 30 which provideselectrical screening.

Although as described above the tubings 26, 28 and 30 are provided asdiscrete items, it is envisaged that the functions carried out therebymay be effected by a reduced number of tubings, as set out, for example,in U.K. Patent No. 2,042,818, where co-extrusions are disclosed.Furthermore, it is envisaged that the sealant material, as exemplifiedby the mastic 34, 36, may be provided integrally with one of thepolymeric members, for example by being provided as an internal coatingon the second polymeric member, exemplified by the tubing 26.

The viscosity of the mastic 34, 36 is selected so that it issufficiently fluid at its application temperature to ensure good sealingagainst cable oil around the ends of the tubes 22 and 24, and yet suchthat at the normal operating temperature, of about 70° C., of the cable,its viscosity, generally between 1×10⁴ and 2×10⁵ Pa-sec, is such that itmaintains sealing against outward pressure of the oil within the cable.In this respect it is noted that pressure can arise in an MI cableeither as a static head pressure resulting from installation of thecable in undulating areas, or from terminal boxes mounted high ontransmission line poles, or as pressure arising due to thermal expansionof the compound in the cable during heating cycles in operation.Furthermore, it will be noted that sealing against the oil is effectedboth by the oil-resistant mastic and also by the directpolymer-to-polymer sealing along the oil barrier tube 23.

Referring to FIG. 1A, part of a cable core 100 is shown of a single core24 kV MI cable, which is of a modified construction from the core 2 ofFIG. 1. For convenience, only part of the joint is shown where itdiffers from the joint shown in FIG. 1. In this arrangement, theconductive tubing 24 of the cable core 2 is not required.

The core 100 is stripped back to reveal a portion of the insulatingimpregnated paper 102, and a portion of the lead or aluminium sheath104. Recoverable oil barrier tubing 106, for example of the samematerial as tubing 23, is recovered to extend over the paper 102 andsheath 104, the preferred latter overlap being between about 40 mm and60 mm. Oil resistant mastic 108 and 110, for example of the samematerial as the mastic 34, is applied at the ends of the tubing 106, andrecoverable stresscontrol tubing 112, for example of the same materialas the tubing 26, is recovered to overlap the sheath 104, encompass thesealant material 108 and tubing 106 and to extend over the sealantmaterial 110 and on across the joint.

The amount of mastic 108 applied is preferably such that, after recoveryof the tubing 112, it extends axially along the sheath 104 for betweenabout 10 mm and 20 mm. Furthermore, the direct polymer-to-polymer axialoverlap between the stress-control tubing 112 and the oil barrier tubing106 is preferably between about 19 mm and 40 mm as described withreference to FIG. 1, but may be increased by up to about 30 mm.

The remainder of the joint is constructed as described above withreference to FIG. 1.

Referring to FIG. 2, there is shown a break-out and joint arrangementfor connecting the cores of a threecore cable 40 to respective ones ofthree identical single cores 42.

The oversheath 44 of the cable 40 is stripped back to reveal a portion46 of the steel armour of the cable. A plumb 48 is formed at the end ofthe armour 46 and three flat metallic braids 50 (only two of which areshown) extend therefrom to provide earth continuity to respective onesof the armour 52 of the cores 42. A heatrecoverable three-outletelectrically-conductive break-out 54 is recovered over the end of thecable 40 so as to arrange the three cores 56 projecting separatelytherefrom. The three cores 56 are electrically connected to the threecores 42 in any convenient manner, depending upon the type and voltagerating of the cable 40 and cores 42.

A tinned copper mesh screen 58 is provided around each of the threejoints and is electrically connected at one end to the plumb 48 on thecable 40 and at the other end to the armouring 52 of each of the cablecores 42. A semiconductive heat-recoverable polymeric tubing 60 is thenrecovered around respective ones of the joints and arranged to overlapat the cable 40 end, respective outlets 62 (only two of which are shown)of the break-out 54, and, at the other end, respective ones of the PVCsheaths 64 of the cable cores 42. The tubings 60 provide furtherprotection over the joint regions of the three cable cores. Finally, afurther heat-recoverable polymeric tube 66, sold under the Raychem TradeName XCSM, is recovered so as to extend from an overlap with theoversheath 44 of the able 40, over the armour 46, the plum 48, theconductive break-out 54, and to overlap the adjacent ends of each of thethree tubings 60. To assist in the sealing of the tube 66 on to thetubing 60 in the region of the break-out outlets 62, mastic sealantmaterial 68 is disposed around the outlets in the regions of the ends ofthe tubings 60, and, in particular, in the crutch 70 therebetween.

The break-out arrangement thus provided, in particular whereby the coresof a multi-core cable are separated and sealed, by the break-out, toprovide three individual cores that are then separately jointed,requires the use of only one break-out component. The arrangement thusnot only simplifies assembly, but also allows the jointed cores to beseparated, thereby to improve heat dissipation inuse.

I claim:
 1. A method of sealing an end of a mass-impregnated paperinsulated cable, the cable sheath being stripped from the end of thecable to expose a length of the mass-impregnated paper insulation and toexpose a conductor of the cable, said method comprising:(a) positioninga first dimensionally recoverable polymeric sleeve such that it overliesthe end region of the cable sheath, the adjacent portion of the massimpregnated paper insulation and the adjacent portion of the conductor;(b) causing the first olymeric sleeve to recover so that it encloses theend region of the cable sheath and the adjacent portion of theinsulation; (c) removing a portion of the first polymeric sleeve toleave the end region of the insualtion unenclosed; (d) applying asealant material over the unenclosed insulation and the adjacent andregion of the first polymeric sleeve; (e) positioning a seconddimensionally recoverable polymeric sleeve such that it overlies thesealant material and the adjacent region of the first polymeric sleevebeyond the applied sealant material; and (f) causing the secondpolymeric sleeve to recover so that it encloses the sealant material andthe adjacent region of the first polymeric sleeve;said first polymericmember and said sealant material being substantially unaffected by themass impregnating material of the cable.
 2. A method according to claim1, wherein the axial length of the overlap between the first and secondpolymeric members is between about 19 mm and 40 mm.
 3. A methodaccording to claim 1 or 2, wherein the overlap between the sealantmaterial and the first polymeric member is between about 15 mm and 25 mmaxially of the cable.
 4. A method according to claim 1, wherein thesecond polymeric member is made of semi-conductive or conductivematerial.
 5. A method according to claim 1, wherein a third recoverablepolymeric member is recovered over the cable to overlap said first firstmember and is sealed thereto.
 6. A method according to claim 5, whereinsealant material applied to effect said sealing between the first andthird members is arranged to overlap the first member by between about10 mm and 20 mm axially of the cable.
 7. A method according to claim 1,in which the sealant material has a viscosity at 25° C. of between about1×10⁶ and 2×10⁵ Pa-sec.
 8. A method according to claim 1, wherein thesealant material is an oil-resistant mastic.
 9. A method according toclaim 1, wherein said insulation is contained within a cable sheath, andwherein said first polymeric member is recovered over a portion of saidsheath adjacent said exposed paper insualtion and is sealed thereto. 10.A method according to claim 9, wherein sealant material applied toeffect said sealing between the first polymeric member and the sheath isarranged to overlap the sheat by between about 10 mm and 20 mm axiallythereof.
 11. A method according to claim 9, wherein said first polymericmember overlaps the sheath by between about 40 mm and 60 mm axiallythereof.
 12. A method according to claim 9, wherein the first polymericmember overlaps said paper insulation by between about 19 mm and 40 mmaxially thereof.
 13. A method according to claim 1, wherein said sealantmaterial is applied integrally with one of said first and secondpolymeric members.
 14. A method of sealing a joint between a first cablecomprising a mass-impregnated paper insulated cable and a second cablecomprising a plastic insulated cable, the sheath of each of said cablesbeing stripped from the end thereof to expose a length of the cableinsulation and to expose a conductor thereof, the conductors of saidcables being electrically connected, said method comprising:(a)positioning a first dimensionally recoverable polymeric sleeve such thatit overlies the end region of the cable sheath of the mass-impregnatedpaper insulated cable, the adjacent portion for the exposedmass-impreganated paper insualtion and the adjacent portion of theconductor; (b) causing the first polymeric sleeve to recover so that itencloses the end region of the cable sheath and the adjacent portion ofthe insualtion; (c) removing a portion of the first polymeric sleeve toleave the end region of the insualtion unenclosed; (d) applying sealantmaterial over the unenclosed insulation, the adjacent end region of thefirst polymer sleeve and the conductors; (e) positioning a second heatrecoverable sleeve such that it overlies the sealant material, theadjacent region of the first polymeric sleeve beyond the applied sealantmaterial and at least a portion of the plastic insulation of said secondcable; and (f) causing the second polymeric sleeve to recover so that itencloses the sealant material, the adjacent region of the firstpolymeric sleeve and at least a portion of the plastic insulation ofsaid second cable;said first polymeric member and said sealant materialbeing substantially unaffected by the mass impregnating material of thecable.